The invention relates to dehumidification systems for interior enclosed spaces.
High levels of heat and humidity cause food items to perish more quickly. This is mainly due to the more rapid proliferation of bacteria and other micro-organisms such as fungi under these conditions. The profitability of businesses that sell perishable foods is directly affected by the length of time that food items can be stored on display shelves that are visible to customers. It is therefore very important to maintain a dehumidified environment in enclosed areas where perishable food items are stored for lengthy periods of time. This is especially the case in a supermarket environment. As well, the refrigeration energy required to operate refrigeration units is reduced with lower humidity levels.
Supermarkets typically rely on air conditioning systems for lowering temperature. These systems often have little or no dehumidifying capability. Typical air conditioning systems combine outside air and return air. This air is then directed to a cooling coil that cools the combined air stream. However, humidity is most concentrated in the outside air. This system is very inefficient for dehumidifying because the more humid outside air is mixed with the return air prior to the dehumidification step. In order for the humidity to be removed, the entire combined air stream needs to cooled down to very low temperatures. In most cases the cooled combined air stream requires re-heating so as not to overcool the space and make it uncomfortable for occupants. This system is an expensive and very inefficient for dehumidification applications.
An improvement to the typical system is provided by a cooling coil bypass. The improved system combines outside and return air streams. However, a portion of the air bypasses the cooling coil. The remainder of the air stream passes over the cooling coil and is cooled down. This method allows for a portion for the air to be cooled to very low temperatures with a moderate amount of cooling capacity.
A disadvantage of this system is that a portion of the air bypasses the cooling coil and is therefore completely untreated. Another disadvantage is that the main source of humidity, the outside air, is diluted and mixed with the return air before the humidity is removed. This is inefficient.
Another improvement was to add a face and bypass damper. This allows better control of the off coil temperatures and air quantities but the main disadvantages of the previous systems persist.
A two coil dual-path system overcomes some of the drawbacks of previous systems. This system has two distinct and dedicated air paths. One air path is for the outside air and the other is for the return air. Each path has its own cooling circuit and coil that operates independently of the other. The dedicated outside air path targets the outside air directly to cool and remove the humidity at the source. A parallel return air path operates similarly. However, the design typically focuses on sensible cooling i.e. strict temperature reduction rather than dehumidification. Once the two air streams have been treated they are then mixed together.
The two coil dual-path system has the advantage of targeting the humidity of the outside air. This provides greater dehumidifying efficiency. However, this system requires a great deal of cooling tonnage to operate. This is a significant drawback that results in elevated operating expense.
There is therefore a need for a dual path dehumidification system that cools and dehumidifies outside air prior to mixing the outside air with return air. There is a need for such a system that is energy efficient and relatively inexpensive to operate. There is a need for such a system that includes a single cooling coil that provides effective cooling results with no cooling coil in the return air path. There is a further need for such a system that is optimized for supermarket application.
The present invention provides a dual path dehumidification system for dehumidifying the interior of a structure. The system dehumidifies outside air separately from re-circulated return air. The system employs a single cooling coil for dehumidifying outside air. The system draws return air from a refrigeration unit located in the structure in order to provide additional cooling.
The system has the advantage that the outside air is isolated for dehumidification and the return air travels along its own dedicated path with no cooling coil. The return air is cooled by the refrigeration units located in the space that is to be dehumidified. The outside and return air streams are mixed only after the outside air stream has been dehumidified. This system has the advantages of a two coil dual-path system, however, total system tonnage is reduced by virtue of the fact that only a single cooling coil is employed. The system is energy efficient and inexpensive compared to previous dehumidification systems.
According to one aspect of the present invention, there is provided a dual path dehumidification system for dehumidifying air and circulating the air through an interior space defined by an exterior structure of a building. The air includes outside air derived from an outside air source and return air from the space. A refrigeration unit is located in the space. The system comprises the following elements:
a supply inlet communicating with said space for passage of dehumidified air to said space;
an outside air path for passage of outside air to the supply inlet, the outside air path communicating between the exterior of the building and the supply inlet, said outside air path being connected to said outside air source;
a cooling unit disposed in said outside air path, the cooling unit including an inlet for receiving outside air and an outlet for flow of cooled and dehumidified outside air to said outside air path;
a return air path for passage of air in the space to the supply inlet, the return air path communicating with the refrigeration unit so that the return air is drawn from the refrigeration unit thereby cooling the return air, the return air path joining the outside air a path at a point between the cooling unit and the supply inlet; and
a fan operatively connected to the outside air path, the return air path and the supply inlet for circulating the air through the outside air path, the return air path and the supply inlet.
According to another aspect of the present invention, there is provided a method for dehumidifying an interior space defined by a building. The interior space has a refrigeration unit. The method comprises the following steps:
providing an outside air path that communicates between an exterior of the building and the space, the outside air path having a cooling unit disposed therein;
delivering outside air from the exterior of the building into the outside air path;
cooling and dehumidifying the air delivered into the outside air path;
delivering the cooled and dehumidified air from the outside air path to the space;
providing a return air path, the refrigeration unit being disposed in the return air path so that return air is drawn from the refrigeration unit;
drawing air through the return air path so that the air is cooled by the refrigeration unit;
circulating the cooled air from the return air path outside of the space; and
joining the cooled air from the return air path to the cooled and dehumidified air from the outside air path to create a combined air steam; and
delivering the combined air steam to the space.